/*	Interactive Gravitational Simulator
	Project: IGS Core
	File: Disk.cpp
	Author: Mike Bantegui <mbante2@gmail.com>, Hofstra University 
	Copyright (C) 2012 - 2013 Mike Bantegui

	This file is part of the IGS software package for simulating
	the N-Body problem in real-time. This was developed as part
	of a departmental honors thesis project at Hofstra University
	in the Spring 2012 semester.

	IGS is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	IGS is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#include "Body.h"
#include "Disk.h"
#include <cmath>

namespace IGS
{

// Destructs the DiskModel
DiskModel::~DiskModel()
{
}

// Creates a system of N bodies in a disk configuration
void DiskModel::Fill(Body *bodies, const int N)
{
	double totalMass = 0;
	const double r = 7;

	for (int i = 0; i < N; i++)
	{
		Vector position = RandomInSphere(r);
		position.z = 0;

		const double R = Length(position);
		const double f = R / r;

		// Add slight bulge towards the center
		position.z = exp(-3 * f * f) * Random(-1, +1);

		// Mass proportional to distance from center
		const double mass = 1 - f;
		totalMass += mass;

		const double theta = atan2(position.y, position.x);
		const Vector velocity = f * Vector(-sin(theta), cos(theta), 0);
		
		bodies[i] = Body(mass, position, velocity);
	}

	for (int i = 0; i < N; i++)
		bodies[i].Mass /= totalMass;
}

}
